gms | German Medical Science

Objectives: Malalignment of the lower limb is presumed to increase the risk for the development and progression of osteoarthritis. Therefore, common concepts in orthopedic surgery aim to restore neutral axis. Nevertheless, little is known about the normal distribution of lower limb alignment in the population. This population-based study was the first to investigate the distribution of mechanical axis in Germany.

Methods: A total of 1985 participants of the Study of Health in Pomerania (SHIP-TREND), a population-based cohort study conducted in the North-Eastern federal state of Mecklenburg-Vorpommern, were included in this investigation. The mechanical axis of 3970 knees was measured on full-body MRI-scans. In addition, participants had to report about knee pain within the last seven days.

Results and conclusion: In this population, 33,6% of the knees were neutrally aligned, 34,3% showed varus and 32,1% valgus alignment. Gender-specific examination showed a neutral mean limb alignment in both sexes, even though women shifted slightly to valgus (+0,5 degrees (SD +2,44 degrees)) while men tended to have varus aligned limbs (-0.86° (+-2.39). The differences got more obvious in the high-grade subgroups resulting in a significantly higher risk for men to have varus and for women to present valgus malalignment.

Knee pain was more often associated with varus alignment; though a significant increase of knee pain was found only in severe high-grade varus deviation.

This study was the first to investigate the distribution of lower limb alignment in Germans. We showed that mechanical axis follows a Gaussian distribution. There is no significant influence of low- and moderate-malalignment on the risk of knee pain. Our findings emphazise the need for a revision of orthopedic standards, giving space for the idea of constitutional and gender-specific „non-neutral-alignment”.